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  #1  
Old 07-04-2013, 11:51 AM
TinCanAlley's Avatar
TinCanAlley TinCanAlley is offline
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Help Identify My New Zenith

Okay, just picked up a new Zenith, but beyond the chassis number, I have no idea what model it is. It looks like an Avanti, but I'm sure it would have such markings somewhere on it.

Also, I'm attaching a few pictures of issues I've discovered. If I have the chassis number correct, Sams Photofacts has the manual for it I can purchase (unless someone knows where I can get one for free). The issues in the pictures are: The center of the image seems stretched. In one picture you can see the person in the center of the screen look normal chest to head and knees to feet, but the entire mid section is stretched. In another image you can see a test pattern that should have a white line, but it is actually showing up as blue and red distortion on the line. In the last two, one is with the Chromatic setting off (looks okay) and the second is with it turned on (orange and loss of detail and most colors).

I'm having trouble setting proper brightness, contrast, color and tint. I've been using Video Essentials like I did with my other Chromacolor 2, but this one is not cooperating. It blooms easily, gets a blue raster when setting the brightness, can't set the color and tint with the test pattern and blue filter. Yellows are more orange than should be, etc.

Anyway, I'm gonna go about cleaning the inside this weekend and sure would love to get this set looking as good as my other Chromacolor 2 you guys have helped me fix up.

Thanks
Attached Images
File Type: jpg New Zenith 1.jpg (48.4 KB, 79 views)
File Type: jpg New Zenith 2.jpg (84.9 KB, 79 views)
File Type: jpg Image Stretch.jpg (80.4 KB, 59 views)
File Type: jpg Color on White Line.jpg (28.1 KB, 46 views)
File Type: jpg Chromatic on.jpg (88.4 KB, 52 views)
File Type: jpg Chromatic off.jpg (72.3 KB, 46 views)
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  #2  
Old 07-04-2013, 03:26 PM
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Electronic M Electronic M is offline
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It is an Avanti(Zenith usually did not put the cabinet name on their sets), and a good one...That if I'm correct is the SS horizontal flat chassis that can keep working come hell fire or high water.

That 'stretched' effect on the image is a vertical linearity issue. The way I see it the entire image above his waist is stretched or the entire area below his waist is compressed(depending on how you look at it). That can likely be cured by feeding a pattern of evenly spaced horizontal bars to the set and adjusting the Vertical height and linearity controls until the spacing of the bars on screen is even(you may have to tweak the vertical centering too).

If it is going blue with different brightness settings then you need to readjust CRT bias. With a blank raster turn the brightness and color level controls to minimum, flip the service switch on the back to collapse the vertical deflection, and turn all the rear screen(sometimes labeled G2) controls to minimum(for this part have a mirror set up so you can watch the set while adjusting the rear controls) then turn red up until a dim red line appears, turn the green back up until you have yellow, and turn the blue back up until you have white, flip the service switch back to normal position to reactivate vertical deflection, and turn brightness up until satisfactory. Now play a gray scale test pattern, and if the gray scale is still tinted there should be some red,green,blue level controls other than the screen controls to adjust tweak those to kill the tint in the monochrome picture. Make sure you also dial in the brightness and contrast to acceptable levels.

After that is done turn the color level up and place a color bars test pattern on the screen and adjust hue and color level for most accurate reasonably saturated color, switch to live action content and tweak hue and possibly color level controls for good skin tones if need be.

The problem with that white line is one of two things. It is either a convergence or usually in curable video design limitation. Get a test pattern with wider monochrome cross hatched bars and see if the bars are color fringed or pure white when displayed. If fringed readjust convergence. If the fringes disappear then what is happening is that the vertical line you were displaying is so thin that the frequency of the pulse representing it is high enough to be above the cutoff of the high pass filter for the chroma circuits and thus cause monochrome noise to leak into chroma circuits. This set predates comb and notch filters so color noise gets into the black and white image and black and white noise gets into the color circuits by the limitations of the design.

There are probably adjustments for the chromatic somewhere. The chromatic was basically just another set of controls for brightness contrast, hue, and color level that could be switched in in place of the user controls so that if someone monkeyed with the user controls and you were in a hurry or you could not get them right your self you could push the button to 'fix it'. The chromatic adjustments drift with time and when you resetup the set like the above screens adjustment I mentioned.
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  #3  
Old 07-04-2013, 04:22 PM
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And make SURE the safety caps in the horiz. out area have been updated...
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Old 07-04-2013, 04:40 PM
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What's with the mess in the general area of the flyback anode cap? I'm wondering if it might have something to do with the problems you're experiencing.
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  #5  
Old 07-04-2013, 06:33 PM
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Before you dig in do 2 things.
1)Clean the crap out of the anode area & anode wires. Pull the
connector off & make the area shiny up to the dag coating.
Do not use anything abrasive. I always used 91% isopropal
alcohol.
2)be sure ALL the 22-5001 safety caps have been changed from
the white ones to the orange drop style. IIRC there are 2 on the
flyback board & 3 under the chassis nearby. Looks like at least
one has been changed.

The chromatic switches to a second set of identical controls &
also affects the tint range. The brightness, contrast, color
& tint controls have hollow shafts. A thin screwdriver adjusts the
chromatic on settings.

After steps 1 & 2 fix the lin problem & get the pix as perfect a B&W
pix as you can THEN turn up the color...........

You are truely blessed. You own what is the best color TV chassis
ever built by anyone, anywhere, at any time. And a remote too !!!!

73 Zeno
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  #6  
Old 07-04-2013, 07:07 PM
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sampson159 sampson159 is offline
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this is the best set ever produced.period.no discussion.and the topper is,its an avanti!lucky guy.the issues are minor,just adjustments.do a quick set up and enjoy the beautiful picture for years to come.dream set for most of us and you got one
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  #7  
Old 07-05-2013, 12:47 AM
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TinCanAlley TinCanAlley is offline
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Okay, lots of responses, so I'll try to respond to all here.

I'm glad it's an Avanti. It's what I've been looking for. Picked it up in Malibu for 50.00.

I purchased the Sams Photofacts for the chassis and did the brightness limiter. I then tried the grayscale adjustments and that's where I ran into an issue. I turned the color control down, turned the red, blue and green fully counterclockwise and set the taps to HI. I then put it into service mode. I was able to get a raster line for the blue and green, but not red. If I turned up the color control, the red line would appear, but wasn't as sharp as the other color lines. Is this normal or is there something I should be looking for that could cause this?

I have a CRT tester and a color bar generator coming on Wednesday. In the mean time, I've vacuumed as much as I can and now need to get in between stuff. Is a soft bristle toothbrush okay for cleaning (no solvent). What are good ways to do the cleaning? Also, is there a way to get the plastic stand a bit more on the white side? I tried a magic eraser, but it didn't work. I think the plastic has yellowed down quite a bit from the surface.

Thanks for the all the great information and advice. I know will all your help she'll be up and going great soon.
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Denon 5803A, Pioneer DVL-700, Pioneer CT-W603RS, Toshiba HD-A3, D-Link DSM-520, Dish VIP-722, Polk 1.2TL, CSi5, LS/fx, RT-800 and PSW-650
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  #8  
Old 07-05-2013, 01:31 AM
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Sounds like you either have a problem with the red G2 control or a bad red gun inside the CRT. I don't recall ever seeing a bad CRT in one of these; but, there's a first time for everything. I do seem to remember the G2 controls would sometimes burn open and you could also have a bad red video output transistor or a dirty transistor socket.
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  #9  
Old 07-05-2013, 01:32 AM
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I just watched an episode of Kojak (on MeTV) in which a Zenith Avanti color TV like yours was featured in an apartment. However, your Avanti is in excellent shape for being well over 35 years old. The white pedestal base on these sets often turns yellow with age, but yours seems to have escaped that, at least for now. Congratulations on finding one of these in nearly pristine condition.

I agree that the 4-lead safety capacitors should be tested and replaced if necessary, before the TV is used any length of time. I don't know how much you know about color-TV high-voltage systems, but one serious problem that can occur with them if the safety capacitor(s) should short or open is that the CRT second-anode voltage will go sky-high, often causing the neck to shear off the tube. I don't know what type of CRT the Avantis used, but if they are rare (or at least difficult to find), it is best to correct any HV problems before the original tube is damaged or destroyed.

Good luck. Your Avanti should give you many years of good service, once the HV safety capacitor(s) are replaced and the area around the second-anode connector is cleaned well. Dirt, dust or other foreign matter in that area of the CRT, especially under the rubber 2nd-anode cap, can and often does cause HV arcing, which in solid-state TVs can destroy parts such as the HV tripler. These may well be NLA (no longer available) for this set at this late date, so anything you can do to keep the original in good shape will be worth the effort.
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Old 07-05-2013, 02:21 AM
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IN the Radio electronics magazine in the 70's, I seem to recall an article by Jack Darr about thie safety cap issue in solid state color tv sets. . I think it was called "how to troubleshoot tuned circuits" or such, and described the cap issue. He claimed some engineer had said on a test in some lab with a failed safety cap--the HV could EXCEED 40 KILOVOLTS!!

Last edited by rca2000; 07-05-2013 at 02:22 AM. Reason: more info
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  #11  
Old 07-05-2013, 07:27 AM
DaveWM DaveWM is offline
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I just repaired the burned G2 Pot on my avanti a little while ago. They are a special pot, plastic snap in body. On mine it was the blue screen, I would go from very blue tint to almost no blue tint in just the slightest movement of the pot.
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Old 07-05-2013, 08:14 AM
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sampson159 sampson159 is offline
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never,ever saw a bad crt in a zenith flat or vertical chassis set.i have one here that is not quite up to par but still makes a fine picture.it tests out at about 60 percent all the way around.look at the crt socket also.post more pictures!
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  #13  
Old 07-05-2013, 10:03 AM
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zeno zeno is offline
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Quote:
Originally Posted by DaveWM View Post
I just repaired the burned G2 Pot on my avanti a little while ago. They are a special pot, plastic snap in body. On mine it was the blue screen, I would go from very blue tint to almost no blue tint in just the slightest movement of the pot.
G-2 pots were a common prob. on the hoz & vert SS chassis & hybrids.
63- 10136,7,&8 IIRC. The vert chassis 19ec45 etc used different
pins but could interchange them all.

73 Zeno
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  #14  
Old 07-05-2013, 10:11 AM
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zeno zeno is offline
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Quote:
Originally Posted by rca2000 View Post
IN the Radio electronics magazine in the 70's, I seem to recall an article by Jack Darr about thie safety cap issue in solid state color tv sets. . I think it was called "how to troubleshoot tuned circuits" or such, and described the cap issue. He claimed some engineer had said on a test in some lab with a failed safety cap--the HV could EXCEED 40 KILOVOLTS!!
Easily. First flat chassis we saw with bad caps the boss told me to plug it in.
It was like a thunderstorm in a box. huge arcs all over the bell &
at the divider which was burned in half. Scared the crap out of me.
New divider & caps & like new again.

73 Zeno
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  #15  
Old 07-05-2013, 10:20 AM
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Quote:
Originally Posted by TinCanAlley View Post
Okay, lots of responses, so I'll try to respond to all here.

I'm glad it's an Avanti. It's what I've been looking for. Picked it up in Malibu for 50.00.

I purchased the Sams Photofacts for the chassis and did the brightness limiter. I then tried the grayscale adjustments and that's where I ran into an issue. I turned the color control down, turned the red, blue and green fully counterclockwise and set the taps to HI. I then put it into service mode. I was able to get a raster line for the blue and green, but not red. If I turned up the color control, the red line would appear, but wasn't as sharp as the other color lines. Is this normal or is there something I should be looking for that could cause this?

I have a CRT tester and a color bar generator coming on Wednesday. In the mean time, I've vacuumed as much as I can and now need to get in between stuff. Is a soft bristle toothbrush okay for cleaning (no solvent). What are good ways to do the cleaning? Also, is there a way to get the plastic stand a bit more on the white side? I tried a magic eraser, but it didn't work. I think the plastic has yellowed down quite a bit from the surface.

Thanks for the all the great information and advice. I know will all your help she'll be up and going great soon.
If you are cleaning the chassis just use a paint brush & vacuum.
Just be careful you dont suck up the plug in transistors.

If the base is solid white plastic you may be able to buff it out.
You can flip the set on its side & experiment on the bottom
assuming its yellowed there to. If you find something that works
take the base off to do it. And if it works tell us !

73 Zeno
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